Intramolecular and Lattice Dynamics in V6-nIVVnVO7(OCH3)12 Crystal

Yu.V. Yablokova, M.A. Augustyniak-Jabłokowa, S. Borshchb, C. Danielcand H. Hartlc aInstitute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland bLaboratoire de Chimie, UMR 5181 CNRS-ENS de Lyon, 69364 Lyon Cedex 07, France cInstitut für Chemie, Freie Universität Berlin, Fabeckstr. 34-36, 14195 Berlin, Germany

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Received: 24 04 2005;

Multi-nuclear mixed-valence clusters V4IVV2VO7(OCH3)12 were studied by X-band EPR in the temperature range 4.2-300 K. An isotropic exchange interactions between four VIV ions with individual spin Si=1/2 determine the energy levels structure of the compound with the total spin states S=0, 1, and 2, which are doubled and split due to the extra electron transfer. The spin-Hamiltonian approach was used for the analysis of the temperature dependences of the EPR spectra parameters and the cluster dynamics. Two types of the electron transfer are assumed: the single jump transfer leading to the splitting of the total spin states by intervals comparable in magnitude with the exchange parameter J≈100-150cm-1 and the double jump one resulting in dynamics. The dependence of the transition ratesνtr on the energy of the total spin states was observed. In particular, in the range 300-220 K the νtr ≈0.7×1010 cm-1 and below 180 K the νtr≈1×1010 cm-1 was estimated. The g-factors of the spin states were shown to depend on the values of the intermediate spins. A phase transition in the T-range 210-180 K leading to the change in the initial VIV ions localization was discovered.

DOI: 10.12693/APhysPolA.108.271 PACS numbers:76.30.Fc, 36.40.Cg